With what you have mentioned here I don't think the problem was you didn't get it hot enough. It is more likely you cooked the feeder too much. It is very easy to do. I have done it. I have had the belly pop open with a awful smell. No wonder my snake wouldn't eat it.
I myself prefer to let the feeder air thaw out for 2 of hours sitting on the enclosure letting the smell of the feeder entice my snake. I lay it belly up and after 2 hours I check it and if the belly is nice and soft and pliable (if not I check every 15 min.) then I heat it up with just the hair dryer. I use to use a heat bulb and dome but I found it is way to easy to over heat (cook) it.
If you want to thaw in water instead of using hot water I would use cool faucet water. Which doesn't take long to thaw.